Two piece flexing die holder

ABSTRACT

A two piece die holder comprising an inner annular member (for holding an extrusion die) concentrically mounted and axially movable within an outer annular member. The outer annular member has a thickness dimension and configuration which allows the forward portion thereof to expand in a radially outward direction as the forward portion is forced against material to be extruded under extrusion pressure. With termination of the extrusion pressure, the outer annular member contracts so that the die holder and die can be withdrawn in tact through an extrusion cylinder or container at the completion of the extrusion cycle.

United States Patent 7 [191 Mahns et al.

1 51 May 8, 1973 154] TWO PIECE FLEXING DlE HOLDER [751 Inventors: Maurice W. Mahns; Clark 0. Stockdale, Jr., both of Pittsburgh, Pa.

[73] Assignee: Aluminum Company of America,

Pittsburgh, Pa.

22 Filed: July 29,1971

21 Appl.No.: 167,321

[52] U.S. Cl ..72/468, 72/481 [51] Int. Cl. ..B2lc 3/06, B2ld 37/04 [58] Field of Search ..72/468, 467, 273,

[56] References Cited UNITED STATES PATENTS Mahns ..72/253 Monestam ..72/467 X Primary Examiner-Richard J. Herbst Assistant ExaminerR. M. Rogers Attorney-Elroy Strickland [57] ABSTRACT A two piece die holder comprising an inner annular member (for holding an extrusion die) concentrically mounted and axially movable within an outer annular member. The outer annular member has a thickness dimension and configuration which allows the forward portion thereof to expand in a radially outward direction as the forward portion is forced against material to be extruded under extrusion pressure. With termination of the-extrusion pressure, the outer annular member contracts so that the die holder and die can be withdrawn in tact through an extrusion cylinder or container at the completion of the extrusion cycle.

4 Claims, 1 Drawing Figure Kevv "72/4111 x Patented May 8, 1973 Maurice W Mu Clark 0. Stockdol TWO PIECE F LEXING DIE HOLDER BACKGROUND OF THE INVENTION The present invention relates generally to a die holder for indirect extrusion apparatus, and particularly to a flexible die holder that readily expands when subjected to extrusion pressure.

Heretofore, it has been the general practice in indirect extrusion presses and processes, to remove the die member from a hollow ram supporting the same before the ram was returned and withdrawn through a container confining the billet material extruded. After the ram was withdrawn from the container, the die was reattached to the ram for the next extrusion stroke or cycle of the operation.

The primary reason for this method of operation is the difficulty in returning or retracting the ram with the die in place. During the extrusion cycle the billet material expands against the interior surface of the container as the die is forced against the material. The billet material tends to adhere to the interior surface of the container to form a shell or skull of the billet material. The internal diameter of the container itself expands elastically as a result of the extrusion material pressing against the container.- When extrusion pressure is released, the container contracts, and, with the shell or skull, forms a reduced internal diameter that impedes the withdrawal and return of the die and die holder through the container, i.e., the ram might be withdrawn with the die member in place but withdrawal requires a substantial amount of force, resulting in an increase in the size and strength of die holding structures attached to the ram, both of which add substantially to the cost of the apparatus as well as reducing the size of the bore in the ram. The reduced bore, in turn, limits the over-all size of the extrusion or number of extrusions that can pass through the ram.

The withdrawal of the die also causes some of the skull adhering to the container surface to return with the die. This returned skull must be removed to prevent problems of skull build-up and jamming between the ram and the inside surface of the container. For these reasons, it has been the practice, as explained above, to remove the die or die holder after the extrusion stroke so that the ram could be returned to its initial position with relative ease and minimum power requirements.

This removal and reassembling of parts, however, required somewhat lengthy periods of time in which no extruded product was being produced so that the savings and advantages attained in the use of lower strength rams and less power were offset by the costly dead cycle time required by the removal of the die and the reassembling process.

Another problem cncountered in indirect extrusion methods and devices is that of trapped air in the container, and the venting of this air from the container. When the die moves against a billet of extrusion material for subsequent extrusion cycles, the die forms a seal with the skull in the contracted container so that air is trapped in the container in an area between the billet and the skull, and exits with the extrusion as the material passes through the die opening. Since the air is between the billet and the container, it leaves the container on or near the surface of the billet material as it is being extruded. This air, as it moves through the container and through the die opening under pressure and at appropriate temperatures, tends to produce un desirable pock marks and blisters on the surface of the extruded product.

Further, trapped air, in combination with lubricants, and under appropriate temperature and pressure conditions, can be ignited to cause explosive damage to the surface of the die opening and to the extruded product.

These problems were generally overcome by the die holder disclosed in US. Pat. No. 3,630,064, granted on Dec. 28, l97l on application Ser. No. 867,492, filed Oct. 20, l969 in the name of Maurice W. Mahns, one of the inventors of the invention presently to be described. The die holder shown and described in the application is a single piece structure adapted to flex radially outwardly when the face thereof engages material to be extruded under extrusion pressure. Such a die, particularly when used in extrusion presses that operate at high extrusion pressures required for extruding hard metals and alloys, must be of high strength to withstand the extrusion pressures. With a single piece die holder, a cross sectional thickness required to provide this high strength results in a relatively stiff structure, the stiffness being such that the diametric expansion of the die holder is not always as great as the elastic expansion of the billet container.

BRIEF SUMMARY OF THE INVENTION The present invention is directed to a die holder comprised of a relatively thick, substantially non-flexing inner annular member (for supporting an extrusion die) and a relatively thin, flexible outer annular member concentrically supporting the inner member. Because of the relative thinness of the outer member, its ability to expand under extrusion pressure is enhanced over that ofthe single piece die holder disclosed in the Mahns application. Because of the rela* tive thickness and strength of the inner member, the inner member handles the major portion of the extruding load. The inner member also assists in spreading the outer member as well as closing any space occurring between the members with expansion of the outer member. This is accomplished by the inner member axially moving relative to the outer member along mating bevelled surfaces of the two members located at the forward ends thereof.

Further, with elastic expansion of the billet container encountered particularly with high extrusion pressure, the outer annular member of the holder can easily be made to equal container expansion.

In addition to these advantages, the die holder of the present invention has all the advantages of the die holder of the above-mentioned patent application, namely, l loading cycle or dead cycle time is substantially reduced since it is unnecessary to remove the die and holder before retraction of the ram, (2') the force required for retraction of the die holder is small thereby allowing the ram and associated structure to be lighter as well as permitting a larger ram opening for larger extruded products, (3) air within the billet container can escape past the die holder during the initial crush of the billet before the die holder reaches its maximum expansion thereby substantially reducing if not eliminating explosion possibilities and the tendency of air blisters to form on the extruded product, and (4) there is no skull to be removed from the die holder upon return of the ram since the die holder contracts to leave a clearance between it and the inside surface of the skull remaining in the container.

The invention, further contemplates a means for loosely interlocking the inner and outer member together without the use of clamps, screws or bolts. This is accomplished by providing one member with a raised or shoulder portion extending into a recess provided in the other member. Clearance is provided between the recess and raised portion so that the inner member can move in the outer member to close the space between the members (along the bevelled surfaces) that occurs with radial expansion of the outer member. I

THE DRAWING The invention, along with its objectives and advantages will best be understood from consideration of the following detailed description in connection with the accompanying drawing in which the sole FIGURE shows a longitudinal section of a die holder constructed in accordance with the principles of the invention.

PREFERRED EMBODIMENT OF THE INVENTION More particularly, the drawing shows in longitudinal section a die holder comprising an outer annular member 12 and an inner annular member 14 concentrically mounted and secured within the outer member. Only one half of the die holder, i.e., one-half of the inner and outer members 12 and 14, is shown in the drawing since the inner and outer members are symmetrical about the center line 15 thereof. Within the inner member an extruding die (not shown) would be mounted for the extruding process.

The outer member has a radially outwardly extending flanged portion 16 which is the forward portion of the member. The forward portion curves inwardly to a relatively thin section 18 adjacent the longitudinal center of the member, and extends rearwardly of the member to a raised portion 20. (The raised portion 20 is used to clamp the die holder to a ram not shown, for example, as shown in the above-mentioned Application, though the present invention is not limited to such clamping means).

The inside diameter of the outer member 12 and the outside diameter of the inner member are essentially constant along the major portion of their lengths, as seen in the drawing. However, at the forward end of the die holder, the inside diameter of the outer member angular increases to provide an inside annular bevelled or inclined surface 22.

The inner member 14 has a relatively thick cross section dimension along its length in comparison to the outer member 12, and a thickened forward end portion 24 providing an annular bevelled surface 26 mating with the bevelled surface 22 ofouter member. As seen in the drawing, the angles of the two bevelled surfaces are not precisely complementary, the resulting difference in inclination ofthe bevelled surfaces providing an annular angular space 28.

The configurations of the forward ends of the inner and outer members is such that the outer member has a relative narrowface 30, and the inner member has a relatively broad face 32.

The inner and outer annular members 12 and 14 are preferably interlocked together by means of a ridge or raised portion 34 provided on the outside diameter of the inner member adjacent a rear face 35 thereof, and a corresponding recess 36 provided in the inside surface of the outer member receiving the raised portion. As shown in the drawing, the recess is made slightly longer than the raised portion, and the overall length of the inner member is slightly less than that of the outer member thereby providing a corresponding clearance space 38 between the rear face 37 of the inner member and the face of an annular tooling block 40 when the front face 32 of the inner member is flush with the front face 30 of the outer member.

The die holder 10, as thus far described, is suitably attached to an extrusion ram (not shown), the tooling block (or blocks) 40 being located between the ram and the die holder.

The operation of the die holder 10 is as follows. When the die holder is forced against a billet or other material contained within a billet container, the inside diameter of the container, as explained earlier, tends to increase elastically because of the pressure against it from thebillet material. Under this same extrusion pressure, a rearwardly directed force is imposed on the faces 30 and 32 of the die holder, and this force produces an opposing force on the rear faces 35 and 37 of the die holder. By virtue of the relatively thin cross section 18 of the outer member 12, in combination with its enlarged outwardly flared forward portion 16, these forces are radially offset on the opposed faces 30 and 35 of the outer member in the manner substantially as indicated in the drawing by arrows l and 2. In this manner, a couple is established in the 'outer member which causes flexing or elastic expansion of the front portion 16 of the outer member in a radially outward direction in an amount sufflcient to close an annular space between it and the expanded inside surface of the container.

When the extruding pressure is terminated, the opposing forces on the outer member 12, and thus the couple, disappear thereby allowing the front portion 16 of the outer member to contract to its original diameter. The die holder is now clear of the interior surface of the container and of any skull material that adheres to the container surface. In this manner, the die holder is free to be easily returned through the container without the time consuming, and thus the costly process, of moving the ram forward until the forward end thereof is completely through and clear of the container. This was done, as explained earlier, to remove the die holder from the ram in order to withdraw the ram back through the container to relocate the die holder on the ram for another extrusion stroke or cycle.

During the extrusion cycle, the inner annular member 14 of the die holder 10 is not required to elastically expand, and thus, as described above, it is a thicker and a stronger member than the outer member 12. With radial expansion of the outer member, the inner member moves toward the tooling block 40 (by virtue of the space 28 existing between the inclined surfaces 22, 26, and the space 38 existing between the tooling block 40 and the inner annular member 14), the movement of the inclined surface 26 of the inner member along the inclined surface 22 of the outer member functioning to close the space occurring between the inner and outer members with radial expansion of the latter. In this manner, billet material is prevented from entering in between the two members.

With contraction of the outer member 12, the bevelled surface 22 thereof engaging the bevelled surface 26 of the inner member 14, moves the inner member forward, the clearance of recess 36 in the outer member allowing the integral raised portion 34 on the inner member to move forward therein.

As can be appreciated, since the outer annular member 12 of the die holder of the present invention is the only portion thereof required to flex, a more flexible die holder is possible than the single piece die holder disclosed in the Mahns application discussed above. The die holder 10, though particularly suitable for high extrusion pressures, is nevertheless employable in presses using intermediate and low pressures thereby providing a more universal die holder.

Further, as noted above, the die holder of the present invention has all the advantages of the single piece die holder of the Mahns application.

From the foregoing description it should now be apparent that a new and useful two piece die holder has been disclosed, the die holder comprising an outer, relatively thin, flexible member and an inner, relatively thick member that is not required to flex but rather moves axially within the bore of the outer member to close the space between the two members that occurs when the outer member expands radially under extrusion pressure.

While the invention has been described in terms ofa preferred embodiment, the claims appended hereto are intended to encompass all embodiments which fall within the spirit of the invention.

Having thus described our invention and certain embodiments thereof, we claim:

1. A die holder for use in an extrusion apparatus, and having a face at one end thereof for engaging a material to be extruded, said die holder comprising an outer annular member of a thickness dimension and configuration that allows it to flex elastically in a radially outwardly direction when said member and the material to be extruded are forced together under extrusion pressure in an extrusion process, and

an inner annular member concentrically mounted within said outer member for holding an extrusion die within an opening in said inner member,

said inner and outer members being axially movable relative to each other, and having mating annular bevelled surfaces respectively providing the inner and outer members with relatively broad and narrow faces for engaging the material to be extruded.

2. The die holder of claim 1 including means for mechanically interlocking the inner and outer annular members together.

3. The die holder of claim 2 in which the means for interlocking the annular members together comprises the mating bevelled surfaces adjacent the face thereof, and an integral shoulder provided on one of the members seated in a mating recess provided in the other member.

4. The die holder of claim 1 in which the outer member has offset faces respectively ex osed to opposmg forces under extrusion pressure suc that a couple 

1. A die holder for use in an extrusion apparatus, and having a face at one end thereof for engaging a material to be extruded, said die holder comprising an outer annular member of a thickness dimension and configuration that allows it to flex elastically in a radially outwardly direction when said member and the material to be extruded are forced together under extrusion pressure in an extrusion process, and an inner annular member concentrically mounted within said outer member for holding an extrusion die within an opening in said inner member, said inner and outer members being axially movable relative to each other, and having mating annular bevelled surfaces respectively providing the inner and outer members with relatively broad and narrow faces for engaging the material to be extruded.
 2. The die holder of claim 1 including means for mechanically interlocking the inner and outer annular members together.
 3. The die holder of claim 2 in which the means for interlocking the annular members together comprises the mating bevelled surfaces adjacent the face thereof, and an integral shoulder provided on one of the members seated in a mating recess provided in the other member.
 4. The die holder of claim 1 in which the outer member has offset faces respectively exposed to opposing forces under extrusion pressure such that a couple is produced in said member to cause radial expansion thereof. 